1. Field of the Invention
The present invention relates to the detection and location of microcalcifications in the human breast with a view to detecting and treating malignant cancer at an early stage.
2. Description of Prior Art
Breast cancer is often characterized by the presence of calcifications along mammary ducts. These may be detected using X-ray mammography. Mammograms do have a number of drawbacks. First, calcifications appear as white objects. Fibroglandular tissue, which is normal in breasts, also appears as white which leads to poor contrast in mammogram images. Second, a mammogram is an extremely uncomfortable procedure. Third, mammography is an X-ray based modality which involves exposure to potentially harmful ionizing radiation. An alternative approach, which does lead to better image quality and diagnosis, is to use magnetic resonance imaging (MRI). However, MRI is prohibitively expensive and could be out of reach for all but limited number of patients with certain socioeconomic standing.
The concept of using ultrasound technology to detect and locate calcifications has in general been developed prior to this invention. The benefit of using ultrasound is that it is portable, relatively cheap and does not expose the patient to harmful radiation. Moreover, in cases with dense breasts, mammograms have proven useless and thus, ultrasound is the only method of choice, next to expensive and unaffordable MRI.
One of the current inventors, Dr. Edmond Rambod, has developed the concept of using ultrasound in conjunction with four or more microphones or sensors located on a ring—or other sensor housing configurations—which is positioned on or around the breast. The acoustic sensors are meant to detect sound radiation radiated from a stimulated target. Since the speed of sound is constant and finite, the signal will arrive at each of the sensors at a different time. If one can precisely estimate the time delays at each sensor then, in theory, one can locate the location of the target. According to Dr. Rambod's invention, a conventional ultrasound transducer (imager or scanner) is used to deliver certain acoustic force to a target and thus, excite a source of acoustic radiation such as a microcalcification. The resulting sound signals are then received by the sensors. Analysis of the data acquired by the sensors and use of certain location paradigms will allow one to determine the location of the target (i.e., microcalcification in the human breast). The inventors of the present invention, including Edmond Rambod, have determined that there is an accurate way to determine the location of an acoustic radiation source such as a microcalcification in a human breast in order to facilitate its classification, biopsy or removal if the microcalcification is proven to be associated with cancer. The following prior art technology is utilized in the present invention:    [1] G. Bretthorst, Bayesian Spectrum Analysis and Parameter Estimation (Springer Verlag, 1989).    [2] J. J. K. Ó Ruanaidh and W. J. Fitzgerald, Numerical Bayesian Methods Applied to Signal Processing (Springer Verlag, 1996).    [3] W. Press, S. Teukolsky, W. Vetterling, and B. Flannery, Numerical Recipes in C (Cambridge University Press, 1992), 2nd ed.    [4] A. Quinn and M. MacLeod, “The distinction between joint and marginal estimators” in “Fourth Valencia International Meeting on Bayesian Statistics” (1991).    [5] A. Quinn, “The performance of Bayesian estimators in the superresolution of signal parameters,” in “IEEE International Conference on Acoustics, Speech and Signal Processing” (1992).    [6] A. Quinn, “Bayesian point inference in signal processing,” Ph.D. thesis, Cambridge University Engineering Department, England (1992).    [7] M. Tanner, Tools for Statistical Inference (Springer Verlag, 1993).    [8] S. Haykin, Communication Systems (NY: Wiley, 1994), 3rd ed.    [9] J. J. K. Ó Ruanaidh, Y. Zhang, P. Emeric, M. R. Swiatek and V. Rozenfeld, “System and method for providing an optical section image by direct phase angle determination and use of more than three images”, U.S. patent application Ser. No. 11/341,935 PCT/US2007/061045 (2006).